Hyperthyroidism is the most common hormonal disorder in cats over 10 years old, causing significant welfare impacts if untreated. Multiple evidence-based treatment options can restore quality of life and extend healthy lifespan.
Hyperthyroidism causes prolonged welfare harm before diagnosis because the signs develop gradually and owners often attribute weight loss or behavioural changes to normal ageing. An affected cat experiences chronic physical discomfort from elevated metabolic rate, potential secondary hypertension causing headache-equivalent states, and cardiovascular strain. Early diagnosis through routine senior screening bloodwork enables treatment before secondary organ damage occurs. Welfare outcomes are excellent with treatment — most cats regain weight, their coats improve, and activity levels normalise. Treatment choice depends on individual circumstances, but radioactive iodine offers a curative single treatment that eliminates the welfare burden of lifelong daily medication.